The present application relates to a micro-fluidic chip, a liquid analysis device in which this micro-fluidic chip can be incorporated, and a flow sending method in this micro-fluidic chip. More specifically, the present application relates to a micro-fluidic chip and so on in which a charged droplet is introduced into a hollow area provided in the micro-fluidic chip and the movement direction of the droplet in the hollow area is controlled based on electric force.
In recent years, development is being advanced on micro-fluidic chips obtained by providing areas and flow channels for performing chemical and biological analysis on a substrate made of silicon or glass by applying microfabrication techniques in the semiconductor industry. These micro-fluidic chips have started to be used as e.g. electrochemical detectors for liquid chromatography and small electrochemical sensors in medical scenes.
The analysis system with such a micro-fluidic chip is referred to as a micro-total-analysis system (μ-TAS), a lab-on-chip, a biochip, and so on, and attracts attention as a technique that allows enhancement in the speed, efficiency, and integration degree of chemical and biological analysis and size reduction of analysis devices.
The μ-TAS is expected to be applied to biological analysis in which a tiny amount of a precious sample or a large number of specimens are treated particularly due to e.g. the reasons that the analysis is possible with a small amount of a sample and disposable (throwaway) chips can be used.
Application examples of the μ-TAS include a microparticle analysis technique in which characteristics of microparticles such as cells or microbeads are analyzed optically, electrically, or magnetically in a flow channel provided on a micro-fluidic chip. In this microparticle analysis technique, fractional collection of a population (group) that satisfies a predetermined condition from microparticles as a result of the analysis is also carried out.
Regarding this microparticle sorting technique, a particle fractionation device employing laser trapping is disclosed in Japanese Patent Laid-Open No. Hei 7-24309. This particle fractionation device irradiates moving particles such as cells with scanning light to thereby give the particles the acting force dependent on the kind of particle and sort the particles.
As a similar technique, a microparticle collection device employing optical force (or optical pressure) is disclosed in Japanese Patent Laid-Open No. 2004-167479. This microparticle collection device irradiates a flow channel of microparticles with a laser beam intersecting with the flow direction of the microparticles to thereby deflect the movement direction of the microparticles that should be collected in the convergence direction of the laser beam and collect the microparticles.
Furthermore, in Japanese Patent Laid-Open No. 2003-107099, a microparticle fractionation micro-fluidic chip having an electrode for controlling the movement direction of microparticles is disclosed. This electrode is disposed near the flow channel port from a microparticle measurement part to a microparticle fractionation flow channel, and serves to control the movement direction of microparticles by interaction with an electric field.